Frequency regulator



' INVENTORS JOHN W LAUR/CELLA WILL/AM 'H. STRACENER fV/VEV- J W LAURICELLA ETAL FREQUENCY REGULATOR Flled June 25 1948 Sept. 5, 1950 Patented Sept. 5, 1950 UNITED STATES PATENT OFFICE Stracener, leaneck, N. 1., assignors to Bendix Aviation Corporation, Teterboro, N. J., a corporation of Delaware Application June 25, 1948, Serial No. 35,104

2 Claims.

The present application relates to a frequency regulator, and more particularly to improvements and simplification of the frequency regulator disclosed and claimed in the copending application Serial No. 783,008, filed October 30, 1947 by John F. Emerson and assigned to Bendix Aviation Corporation.

Heretofore, accurate regulation of the frequency output of a motor driven generator of the type particularly designed for aircraft use has been both desirable and elusive from the standpoint of a practical solution.

Use of a resonant circuit as the frequency sensitive portion of a frequency regulator is not new, but has heretofore in general left much to be desired. For instance, if the current through a resonant circuit is rectified and used directly as motor field current the large amount of D. C. power required would give poor frequency response due to the low Q (ratio of reactance/resistance) and hence the resonant circuit would require large capacity and inductance volt ampere ratings in order to improve the Q. Since the Q of the resonant circuit cannot be above a limiting value, because of the excessive voltages and currents developed at resonance, its frequency sensitivity is limited.

As disclosed herein, by feeding the output of a resonant circuit into a vacuum tube which in turn operates a carbon pile regulator controlling the motor field current, the power drain on the resonant circuit is reduced to a minimum, and small size reactance elements can be used with suitable value of Q.

By providing a capacitor to shunt the inductance of a series resonant circuit, as disclosed herein, the grid and plate voltages of the vacuum tube can be brought into phase below resonance and out of phase above resonance of the series resonant circuit by proper choice of the circuit parameters. Thus, there may be provided in effect a broadly tuned circuit at frequencies below the control point on predetermined operating frequency, but having a sharp slope characteristic which is just above resonance in the control region. This steep slope of the frequency versus plate current curve just above resonance is desirable because it provides many times the control effect for one percent change in frequency than that given by a one percent change in A. 0. line voltage.

It should be noted, however, that in the disclosed arrangement in starting, her with or without the vacuum tube at operating temperatures, full field current is applied to the motor to limit the speed thereof. 7

This full field current is held until the filament of the tube has heated to operating tern.- perature anduntil the speed of the motor-alter: nat'or is such that its output voltage. causes enough plate current to flow to cause the carbon pile resistance to increase, decreasing the motorrfield current, which, in turn, speeds up' themotor until resonantfrequency of the con--. trol circuit is exceeded, whereupon there is a sharp decrease in the regulating current with increasein frequency until the desired operating frequency is attained. At this point the plate current is dropping rapidly with increasing'frd quency and the carbon pile is decreasing in re; sistance, increasing the motor field current'and preventing the motor from further increasing'in speed.

Use in the regulator of a compensating winding connected in series with the motor field and. arranged to aid the main control winding allows high frequency sensitivity with good stability.

Anadditional winding aiding the main control winding and connected acrossthe D. C. supply line for the filament of the vacuum tube reduces the ampere turns required in the main control windingof the regulator.

An object of the invention, therefore, is to provide a novelregulator of the carbon pile type having an auxiliary, electromagnetic winding or coil for applying a biasing force to the armature of the carbon pile regulator to reduce -the,.,am-. pere turns required in a main control winding and thereby increase the sensitivity of the main control winding.

Another object of the invention is to provide a frequency regulator for a motor-generator in which there is provided a frequency sensitive series resonant circuit so selected as to resonate at a frequency slightly less than a predetermined desired operating frequency of the generator and a parallel resonant circuit so selected as to reso nate at a frequency slightly greater than the operating frequency, and sufficiently close thereto as to give a characteristic sharp frequency re sponse at frequencies slightly above or below'the predetermined operating frequency so as to affect a control grid of an electronic valve and thereby'regulate the energization of a contr'ol winding of a variable resistance element so as to maintain the predetermined operating frequency of the generator.

Another ct oithe in ten to provide a control circuit which is errectively a series 3 resonant circuit at below the desired operating frequency of a generator and a parallel resonant circuit at above the desired operating frequency.

Another object of the invention is to provide a control circuit adapted to be connected across the output of an A. C. generator and including a condenser, an inductance and a second condenser connected in series and resonant at a frequenc less than the desired or operating frequency of the generator and a third condenser connected across the inductance which causes in efiect at frequencies in excess of resonance of the series circuit a shunting of the inductance so that the voltage applied across the plate and cathode through the series connected capacitors is less than and is approximately 180 out of phase with the voltage applied across the grid and cathode, and grid and plate through the series connected capacitor and inductance so as to cause a sharp change in the regulating current upon change in the output frequency of the generator to either side of the desired or operating frequency of the generator.

The above and other objects and features of the invention will appear more fully hereinafter from a consideration of the following description taken in connection with the accompanying drawing wherein one embodiment of the invention is illustrated by way of example.

Referring now in detail to the single figure of the accompanying drawing, in which there is shown a schematic wiring diagram of an embodiment of my invention, the numeral I indicates a source of direct current such as a battery connected through conductors 3 and to the armature of a D. C. motor, indicated generally by the numeral I and having a shunt field winding 9 of conventional type. The motor I drives through shaft I I an alternator or generator indicated generally by the numeral l3 and having output lines I4 and I6.

The shunt field winding 9 of the motor 'I is connected at one end to the conductor 3, while the opposite end of the field winding 9 is connected by a conductor I5 to a connector post A of a frequency regulator indicated generally by the numeral I1 and which will be explained in greater detail hereinafter.

'I he alternator I3 has a field winding I9 one end of which is connected to the conductor 5, while the opposite end is connected to one end of a variable resistance element or carbon pile 2| of a voltage regulator of conventional type indicated generally by the numeral 23. The opposite end of the carbon pile 2i is connected to conductor 3 leading to the source of electrical energy I. Thus, the source of electrical energy is connected through the carbon pile 2| to the field winding I9 of the alternator I3.

The voltage regulator 23 is shown diagrammatically as including an armature 25 pivoted at 26 and biased under tension of a spring 28 in a direction tending to decrease the resistance of the pile 2| and increase the energization of the field winding I9 so as to effect an increase in the voltage output of the alternator I3. An electromagnetic winding or coil 30 biases the armature 25 in a direction opposing the spring 28 and tending to increase the resistance of the carbon pile 2| so as to decrease the energization of the field winding I9 and thereby decrease the output voltage of the alternator I3.

The control coil 36 is connected by line 3I and 33 to the output of a rectifier 35 of conventional type and having input lines 31 and 38 connected to the output lines I4 and I5 of the alternator I3. It will be seen from the foregoing that the voltage regulator 23 regulates the field winding I9 of the alternator I3 so as to maintain a substantially constant voltage across the lines I4 and I6 which lead to a load indicated schematically by the numeral 40.

Upon change in the load 40 across the output lines of the alternator I3 the output voltage will tend to change together with the speed of motor I bringing into operation the novel frequency regulator indicated generally by the numeral I'I.

Frequency regulator circuit The frequency regulator circuit includes a variable resistance carbon pile element 50 of a regulator 5|. One end of the resistance 50 is connected by a conductor 52 to a connector post C from which there leads a conductor 53 to the conductor 5 and thereby to the source of electrical energy I. The opposite end of the carbon pile element 50 is connected by a conductor 55 to one end of a compensating winding 51. The opposite end of the compensating winding is connected through a conductor 59 to the connector post A which is connected to the motor field winding 9 through conductor I5. 9

The regulator 5|, described and claimed in divisional application Serial No. 139,756, filed January 20, 1950, is shown diagrammatically as including an armature SI pivoted at 63 and biased under tension of a spring 65 in a direction tending to decrease the resistance of the carbon pile element 50. Carried by the regulator 5| are three windings or coils, including the compensating winding 51, a main control winding 61 and a novel auxiliary winding 68. All of these windings or coils act in aiding relation one to the other and, in normal operation, the accumulative effect of the windings tends to bias the armature BI in a direction opposing the spring 65 and tending to increase the resistance of the carbon pile 63 so as to decrease the energization of the shunt field 9 and thereby increase the speed of the motor I.

Controlling the energization of the main control winding 6! is a multi-element electronic valve 69. The electronic valve 69 includes a plate or anode element II, a control grid element I3, a cathode element I5, a heater element TI and a shield grid IS. The plate element II and shield grid 19 are connected by conductor 8I to one end of the main control winding 61.

The opposite end of the main control winding 6! is connected by a conductor 83 to a connector post D from which leads a conductor. 85 to the output line I4 of the alternator I3. A capacitor 8! is shunted across the main control winding 51 so as to reduce the effective load impedance in the plate circuit and store energy during the effective half-waves to smooth out current pulsations in the main control winding 61. The cathode element I5of the electronic valve 69 is connected-by a conductor 89 to the connector post E from which leads the conductor 91 to the output line I6 of the alternator I3.

Also connected across the conductors 83 and 89 leading from the output of the alternator I3 is a control circuit I00 including a conductor I02 leading from conductor 83, a capacitor I04, inductance I06, capacitor I08 and a. conductor IIO leading to conductor 89 and forming a series resonant circuit. shunted across the inductance I06 is a capacitor. II2 forming with inductance I00 a parallel resonant circuit.

The conductors I02 and H0 lead from the cenductors 83 and as respectively and connect the control circuit Hill across the output. lines I4 and I 6 of the alternator I3. A conductor II4- leads. from an output tap I Is in inductance I06 through resistor I I8 to the control grid I3 of the electronic valve 69. The resistor I I8 serves to limit the grid current to. a Safe value.

Connected across the conductors 89 and H4 is a further resistance element I which provides a D. C. return for the grid current and with resistor I I8 serves to provide proper phasing of grid potential relative to plate potential.

It will be seen from the foregoing that the plate II of the electronic valve 69 is fed with raw A. C. through the main control coil 6'! so that the electronic valve 69 functions as an A. C. power halfwave rectifier and as a frequency responsive regulating device, since the output of the control circuit I80 is fed directly to the control grid I3 of the electronic valve 89 by conductor I I4.

A further novel feature, described and claimed in divisional application Serial No. 139,756, filed January 20, 1950, is the arrangement of the auxiliary coil 68 one end of which is connected through conductors 52, 53 and 5 to one terminal of the source of electrical energy I, while the opposite end of the auxiliary winding 68 is connected by a conductor I22 to connector post B and through the conductor I24 to conductor 3 and the opposite terminal of the source of electrical energy I.

Shunted across the conductors 52 and I22 through conductors I25 and I21 is the heater element H. The armature Bl under the biasing force of spring 65 tends to hold the pile in its fully compressed position so that full field current is applied to the motor field 9 limiting the speed of the motor until the filament H has reached its operating condition and sufficient current is passed to the main control winding 81 to decrease the resistance thereof.

The winding 68 aids the main control winding 5'! and reduces the ampere turns required in the main control coil tI. Thus, the ampere turns of the main control winding ET is materially reduced causing a corresponding increase in the sensitivity of the main control coil 61 to changes in frequency as reflected through the electronic valve 69.

The resonant frequency of the series resonant circuit is designed so as to be somewhat less than the desired or regulated operating frequency or speed of the motor driven generator I3. Further, the shunting capacitor H2 is so selected that at frequencies in excess of the resonant frequency of the series circuit the voltage applied to the plate and cathode from across the series connected capacitors I88, H2 and IE4 is less than that applied through output tap H6 by the inductance I63 and capacitor I118 across the cathode and grid, or by the inductance I06 and capacitor I04 across the grid and plate and is out of phase therewith by approximately 180 so that the grid :73 is so biased as to effect a sharp decrease in the plate current at the frequencies just above resonance and in the control region. This steep slope of the frequency versus plate current curve is desirable because it provides a greater control effect for change in frequency. Thus, upon changes in the frequency to one side or other of the desired operating frequency of the generator I3, a sharp regulator effect is produced tending to adjust the carbon pile 58 so as to bring the speed of the motor I back to the desired operating value.

In other words, the series resonant circuit including capacitor its, inductance Hit, and capaciton Hi8- seselected that it will resonate at a frequency slightly less than the desired operating frequencyof the generator, moreover the capacitor- N2 of the parallel resonant circuit isselected' of such a value that the parallel resonant circuit will 'resonate at a frequency slightly greater than the desired operating frequency of the generator, but sufficiently close as to give a sharp characteristic or frequency response at frequencies slightly above or belovt the desired operating frequency for which the regulator is set to maintain.

Thus the control circuit I'Ilfl is effectively a series resonant circuit at below the desired operating frequency and a parallel resonant circuit at frequencies above the desired operating frequencies.

The energization of the main control winding El is regulated through the electronic valve 69 and the highly sensitive winding 67 is stabilized by the compensating winding 51. A decrease in the energization of winding 61 tending to decrease resistance 59 will cause a corresponding increase in the energization of the compensating winding 5'! which will tend to retard further change in the resistance of the carbon pile 50 so as to provide stability in the control. Likewise, an increase in the energization of the winding 67 tending to increase the resistance of the carbon pile 5% will decrease the energization of the compensating winding 51 so as to tend to retard further increase in the resistance of the pile 50.

Thus, the compensating winding 51 provides stability in the regulator, while the arrangement of the auxiliary winding 68 in relation to the winding 6'! permits fewer turns in the winding 67 than would otherwise be necessary so that the winding 6! may have greater sensitivity to changes in the plate current so as to provide the regulator with high frequency sensitivity.

Although only one embodiment of the invention has been illustrated and described, various changes in the form and relative arrangements of the parts may be made to suit requirements.

What is claimed is:

1. For use with a variable speed generator having a pulsating output current, the frequency of which varies with the speed of the generator, the combination comprising an electronic valve including an anode, a cathode and a control grid; a series tuned circuit including a first capacitor, a second capacitor, and an inductance serially connecting the first and second capacitors; a second parallel tuned circuit including a third capacitor connected in shunt relation to said inductance, said series tuned circuit connected across the anode and cathode of said electronic valve, said inductance tapped at a point intermediate its opposite ends, a conductor leading from said tapped point directly to the control grid, connecting means adapted to connect said anode and cathode across the output of said generator, said connecting means including an electromagnetic winding to regulate the speed of said generator to a predetermined operating frequency in response to electronic flow from the cathode to the anode, said series tuned circuit having a resonant frequency slightly less than said operating frequency, and said parallel tuned circuit having a resonant frequency slightly greater than said operating frequency so as to effect a sharp response in said winding upon application of the output current to said tuned circuits at frequencies above or below the operating frequency and within the range limited by erated by the first mentioned winding to regulate 5 the frequency of said generator, and an auxiliary electromagnetic winding to apply a constant biasing force to augment the biasing force of said first mentioned winding, and said first winding highly sensitive to changes in electronic flow from 10 said cathode to said anode.

JOHN W. LAURICELLA. WILLIAM H. STRACENER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,001,557 Von Ohlsen May 14, 1935 2,036,488 Moore Apr. 7, 1936 

